With each generation, wireless communication systems are characterized by ever-higher data rates. While some increase in data rates may be attributed to improvements in modulation, coding, and the like, significant increases in data rates generally require higher system bandwidths. For example, the IMT advanced, a proposed fourth generation (4G) wireless communication system, contemplates bandwidths up to 100 MHz. However, the radio spectrum is a limited resource. Since many operators and systems compete for limited radio resources, it is unlikely that 100 MHz of contiguous spectrum will be free for such systems.
One approach to increasing bandwidth requirements in limited, fragmented spectrum is to aggregate non-contiguous spectrum, as depicted in FIG. 1. From a baseband point of view, this can effectively increase system bandwidth sufficiently to support up to 1 Gb/s, a throughput requirement for 4G systems. Transmitting data in non-continuous parts of the spectrum also introduces flexibility, as spectrum utilization may be adapted to existing spectrum use and geographical position. Additionally, different modulation and coding schemes may be advantageously applied to different portions of the spectrum.
A possible evolution of current cellular systems, such as the 3GPP Long Term Evolution (LTE), to support non-contiguous spectrum is to introduce multiple component carriers. In a multiple component carrier system, each separate portion of spectrum may be considered a Release 8 LTE system. A 4G mobile terminal will in such a case be capable of receiving multiple LTE carriers, of different bandwidths, and transmitted at different carrier frequencies, and in such a terminal new problem areas may be introduced.